Accurate and reliable cost estimating and cost analyzing techniques are essential in all types of parts manufacturing and fabrication. For example, advanced composite materials are invaluable in designing structures for high performance environments. Their unique mechanical properties make it possible to engineer structures that meet performance requirements (stiffness, strength, etc.) at a lower weight than counterpart designs made of metal. However, advanced composites are very expensive to manufacture, to the point that fabrication cost is currently a major issue affecting the ultimate widespread use of these materials. Numerous research efforts have investigated thermoset composite fabrication processes from various viewpoints and arrived at similar conclusions on how to reduce the high cost of manufacturing composite structures. There is a general consensus that several areas can play a key role; these include part design, materials selection, and cost effective manufacturing processes and automated systems. In all three of these areas, manufacturing cost estimation techniques are needed as a tool for increasing cost effectiveness.
Part designers for all kinds of parts need to design parts and components with manufacturing cost effectiveness in mind. Studies in Concurrent Design and Concurrent Engineering (CD/DE) indicate that a large percentage of the final cost of a product is determined in the early phases of the product life cycle (i.e., the design phase as opposed to production phase); hence it is here that the "window of opportunity" for cost reduction is the largest. However, in order for a designer to design with manufacturing cost in mind from the start, he or she needs a method of estimating how each part feature might affect the total manufacturing cost of the part. For example, a tight radius or steep angle designed into a part immediately imposes limits on the set of feasible processing options which can be designed into a part and on the set of feasible processing options which can be used to make the part. This in turn sets the bounds on final part cost. Ideally, part features which require expensive fabrication processes should be eliminated if possible early in the design phase.
Material selection also plays a large part in cost, not only because the raw material itself is so expensive but also because the material selected often determines downstream manufacturing costs. There are many cases where more than one material can meet the structural and/or weight requirements specified for a given part. For example, in the case of fabrication for an advanced material composite, assume there is a choice between a unidirectional tape and broadgoods from the same resin-impregnated (prepreg) material. Clearly there is a difference in the costs of these raw material forms; uni-directional prepreg materials are less expensive because the material supplier has not gone through the added step of weaving the broadgoods fabric. At the same time, in general it takes more labor to build up a laminate from unidirectional material than to build it up using broadgoods. Therefore there is a tradeoff between actual raw material costs and the downstream manufacturing costs which are predetermined in choosing a particular raw material. It is important in selecting materials to be able to quantitatively estimate the costs of this tradeoff in order to choose the material that will be the most cost effective overall.
Manufacturing cost estimation techniques are just as important to a machine designer or process engineer as they are to a part designer or material selection team. When designing automated machinery or new fabrication processes, system designers must consider the overall costs of the existing operations they expect to replace. One study of fabrication processes suggests that past efforts to automate the processes were not cost effective in comparison with manual layup since the reduction of direct labor costs did not exceed the capital investment in equipment. To insure that any effort to develop automated manufacturing equipment will produce a machine that is cost effective, the designer must understand a priori where and how manufacturing costs are incurred and what factors drive the cost of the final manufactured part.